JP7063067B2 - Droplet ejection device - Google Patents

Description

The present invention relates to a droplet ejection device.

Conventionally, there is a liquid ejection device that ejects a liquid such as ink from a recording head toward a recording medium. The recording head has a manifold for storing the liquid and a plurality of pressure chambers for distributing the liquid from the manifold. Nozzles are communicated with the pressure chamber. Then, when pressure is applied to the liquid in the pressure chamber, the liquid is discharged from the nozzle.

Further, in the recording head, a plurality of pressure chambers sharing the manifold are arranged in a row. In this case, the pressure chamber located in the middle of the row is sandwiched between the pressure chambers on both sides. On the other hand, the pressure chamber located at the end of the row has the other pressure chamber on only one side. Therefore, the discharge characteristics differ between the pressure chamber in the middle of the row and the pressure chamber at the end of the row due to the difference in the peripheral structure.

Therefore, a recording head in which a dummy pressure chamber is provided outside the pressure chamber at the end of the row has been proposed (see Patent Document 1). As a result, the pressure chamber at the end of the row and the pressure chamber in the middle of the row have similar peripheral structures to each other, so that the discharge characteristics are also the same.

Japanese Unexamined Patent Publication No. 2015-037863

By the way, in the recording head of Patent Document 1, in order to further align the discharge characteristics, not only the peripheral structure is made similar, but also the drive potential is continuously applied to the piezoelectric element corresponding to the dummy pressure chamber. This is also done when the dummy pressure chamber is not filled with ink.

However, if the piezoelectric element is driven in a state where the dummy pressure chamber (non-discharge pressure chamber) is not filled with the recording liquid such as ink, the piezoelectric element is excessively deformed, resulting in a failure (for example, damage to the piezoelectric element). There was a problem that there was a risk of connection.

The present invention has been made to solve such a problem, and an object of the present invention is to suppress excessive deformation of the piezoelectric element due to the non-discharge pressure chamber not being filled with the recording liquid.

The present invention has been made to solve the above-mentioned problems, and the droplet ejection device according to the present invention has a plurality of ejection pressure chambers arranged in a row and a direction in which the plurality of ejection pressure chambers are arranged. A flow path member in which a pair of non-discharge pressure chambers arranged with the plurality of discharge pressure chambers interposed therebetween is formed, and a pulse-shaped first drive voltage is provided corresponding to each of the plurality of discharge pressure chambers. A recording having a plurality of first piezoelectric elements to which The pair of non-discharge pressure chambers provided with a head are not filled with recording liquid, and at least one of the falling time and the rising time of the two drive voltages is the first piezoelectric element adjacent to the second piezoelectric element. The first drive voltage applied to is longer than at least one of the fall time and the rise time corresponding to at least one of the fall time and the rise time of the second drive voltage.

The present invention has an effect that excessive deformation of the piezoelectric element due to the fact that the recording liquid is not filled in the non-discharge pressure chamber can be suppressed.

FIG. 1 is a schematic diagram showing a schematic configuration of a droplet ejection device according to the first embodiment of the present invention. FIG. 2 is a block diagram showing a functional configuration of the droplet ejection device. FIG. 3 is an enlarged plan view showing a part of the recording head. 4A and 4B are enlarged cross-sectional views showing a part of the recording head, where FIG. 4A shows a discharge pressure chamber and FIG. 4B shows a non-discharge pressure chamber. 5A and 5B are diagrams showing the electrical configuration of the recording head, FIG. 5A is a circuit diagram showing the drive circuits of the first and second piezoelectric elements, and FIG. 5B is a circuit diagram showing the drive circuits of the first and second piezoelectric elements, and FIG. 5B is applied to the first and second piezoelectric elements. It is a waveform diagram which shows the waveform of the drive voltage which is made. 6A and 6B are diagrams showing an equivalent circuit of the drive circuit of the first and second piezoelectric elements, FIG. 6A is a circuit diagram showing an equivalent circuit of the drive circuit of the first piezoelectric element, and FIG. 6B is a circuit diagram showing the equivalent circuit of the drive circuit of the first piezoelectric element. It is a circuit diagram which shows the equivalent circuit of the drive circuit of a piezoelectric element. 7A and 7B are plan views schematically showing individual electrodes of the piezoelectric element, FIG. 7A is a plan view schematically showing individual electrodes of the first piezoelectric element, and FIG. 7B is an individual of the second piezoelectric element. It is a top view which shows the electrode schematically. FIG. 8 is a diagram showing the drive voltage applied to the piezoelectric element corresponding to the pressure chamber not filled with the recording liquid and the displacement of the piezoelectric element. 9A and 9B are views schematically showing the configuration of the vicinity of the piezoelectric element of the recording head of the recording head of the droplet ejection device according to the second embodiment of the present invention, FIG. 9A is a plan view, and FIG. 9B is a sectional view. Is.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In the following, the same or corresponding elements are designated by the same reference numerals throughout all the drawings, and the overlapping description thereof will be omitted. Further, the present invention is not limited to the following embodiments.

(Embodiment 1)
As the recording head and the droplet ejection device according to the first embodiment of the present invention, the ink ejection device for ejecting ink to the recorded sheet will be described below as an example. However, the liquid discharged by the droplet ejection device according to the present invention is not limited to ink, and the target to which the ejected liquid adheres is not limited to the sheet-like one. Further, the droplet ejection device is not limited to the ink ejection device, and may be any device that ejects the recording liquid to the recording medium.

[Configuration of Droplet Discharge Device]
FIG. 1 is a schematic diagram showing a schematic configuration of a droplet ejection device. The droplet ejection device 1 is assembled with a paper feed tray 10, a platen 11, and a carriage 12 in this order from the bottom. The paper feed tray 10 accommodates a plurality of recorded sheets P. Above the paper feed tray 10, a platen 11 having a long length in the left-right direction is provided. The platen 11 is a flat plate member and supports the recorded sheet P to be conveyed from below. A carriage 12 is provided above the platen 11. The carriage 12 can be reciprocated in the left-right direction, and is equipped with a recording head 13 and the like. Further, a paper ejection tray 14 is provided in front of the platen 11, and receives the recorded sheet P for which recording has been completed.

A sheet transport path 20 extends from the rear of the paper feed tray 10. The sheet transport path 20 connects the paper feed tray 10 and the paper output tray 14. The sheet transport path 20 can be divided into three paths: a curved path 21, a straight path 22, and an end path 23. The curved path 21 curves upward from the paper feed tray 10 and reaches the vicinity of the rear of the platen 11. The straight pass 22 reaches from the end point of the curved pass 21 to the vicinity of the front of the platen 11. The end pass 23 reaches from the end point of the straight pass 22 to the output tray 14.

The droplet ejection device 1 includes a feeding roller 30, a transport roller 31, and a discharge roller 34 as a sheet transport mechanism for transporting the recorded sheet P. The sheet transport mechanism transports the recorded sheet P of the paper feed tray 10 to the paper output tray 14 along the sheet transport path 20.

Specifically, the feeding roller 30 is provided directly above the paper feed tray 10 and is in contact with the recorded sheet P from above. The transport roller 31 is combined with the pinch roller 32 to form the transport roller portion 33, and is arranged near the downstream end of the curved path 21. The transport roller portion 33 connects the curved path 21 and the straight path 22. The discharge roller 34 is combined with the spur roller 35 to form the discharge roller portion 36, and is arranged near the downstream end of the straight path 22. The discharge roller portion 36 connects the straight path 22 and the end path 23.

Here, the recorded sheet P is supplied to the transport roller unit 33 by the feed roller 30 via the curved path 21. Further, the recorded sheet P is fed from the straight pass 22 to the discharge roller unit 36 by the transport roller unit 33. In the straight pass 22, ink is ejected from the recording head 13 to the recorded sheet P on the platen 11. An image is recorded on the recorded sheet P. The recorded sheet P to be recorded is conveyed to the paper output tray 14 by the discharge roller unit 36.

FIG. 2 is a block diagram showing a functional configuration of the droplet ejection device 1. The control unit 40 of the droplet ejection device 1 includes a first substrate and a second substrate. The CPU 41, ROM 42, RAM 43, and EEPROM 44 are mounted on the first board, and the ASIC 45 is mounted on the second board. Two motor driver ICs 46 and 47 and a head driver IC48 are connected to the ASIC 45. The motor driver IC 46 drives the transfer motor 50, and the motor driver IC 47 drives the carriage motor 51. The head driver IC 48 drives the piezoelectric elements 71 and 81 (described later) of the recording head 13.

When the liquid discharge device 1 receives a print job input from a user or another communication device, the CPU 41 outputs a print job execution command to the ASIC 45 based on the program stored in the ROM 42. The ASIC 45 controls each driver IC 46 to 48 based on this command. As a result, recording processing such as feeding and transporting the sheet to be recorded P, ejecting ink synchronized with this transport, and the like is executed.

Specifically, the motor driver IC 46 drives the transport motor 50 to rotate the feed roller 30, the transport roller 31, and the discharge roller 34. The motor driver IC 47 drives the carriage motor 51 to reciprocate the carriage 12 in the left-right direction (main scanning direction). The head driver IC48 drives the piezoelectric element to vibrate the meniscus and eject ink.

Of these, the drive voltage output by the head driver IC 48 is a pulse-shaped signal that changes between the first potential v1 and the second potential v2 different from the first potential v1. When the drive voltage is the first potential v1, the pressure chamber becomes the first volume V1, and when the drive voltage is the second potential v2, the pressure chamber becomes the second volume V2 smaller than the first volume V1 (V1> V2). ). In this way, the piezoelectric element is displaced by the application of the drive voltage, and the volume of the pressure chamber changes accordingly.

Further, the liquid discharge device 1 includes various sensors (for example, a tip detection sensor for detecting the position of the recorded sheet, an encoder for detecting the position of the carriage, and the like). The control unit 40 controls each driver IC 46 to 48 based on the signals from these sensors, and forms an image on the recorded sheet P.

[Recording head configuration]
FIG. 3 is an enlarged plan view of a part of the recording head 13. The recording head 13 includes a manifold 60 for temporarily storing ink and an ejection channel 70 for distributing ink from the manifold 60. The manifold 60 is a space that is long in the front-rear direction (sub-scanning direction) and has a rectangular parallelepiped outer shape. The recording head 13 includes a dummy channel 80 in addition to the discharge channel 70. No ink is distributed to the dummy channel 80.

When looking downstream from the manifold 60 (nozzle side on which ink is ejected), the size of the manifold 60 is the largest. Therefore, when compared in terms of the component units of the flow path (for example, the manifold 60, the discharge pressure chamber 73, the descender 74, the discharge nozzle 75, etc.), the flow path resistance to the ink is the smallest in the manifold 60. A supply path extending from a liquid tank (not shown) is connected to the rear portion (upstream end portion) of the manifold 60.

As shown in FIG. 3, the recording head 13 is arranged with a discharge channel 70 and a dummy channel 80. Of these, each discharge channel 70 has a partial vertical overlap with the manifold 60, and is arranged on one side (right side in FIG. 3) of the left and right sides of the manifold 60. The dummy channel 80 does not overlap with the manifold 60. Further, the channels 70 and 80 are arranged at equal intervals in the front-rear direction along the manifold 60 to form a channel row. At this time, the dummy channel 80 is located at the end of the channel row.

FIG. 4 is an enlarged cross-sectional view of a part of the recording head 13. 4 (a) is a cross-sectional view of the discharge channel 70 cut along the line IVa-IVa in FIG. 3, and FIG. 4 (b) is a cross-sectional view of the dummy channel 80 cut along the line IVb-IVb in FIG. 4 (a) and 4 (b) are also cross sections intersecting the longitudinal direction of the manifold 60.

As shown in FIG. 4, in the discharge channel 70, the communication flow path 72 vertically overlaps with the manifold 60. The dummy channel 80 does not have a similar communication flow path. However, the other flow path components have in common that they are connected in the order of pressure chamber, descender and nozzle. Further, the pressure chamber is also the same in that a part of the wall portion thereof is composed of a piezoelectric element.

The piezoelectric element is a laminate of a piezoelectric layer and a diaphragm. Electrodes (individual electrodes and common electrodes) are laminated on the front and back of the piezoelectric layer, and the piezoelectric layer expands and contracts in the plane direction (direction orthogonal to the vertical direction) when a driving voltage is applied. Since the diaphragm does not deform spontaneously, the piezoelectric element is displaced toward the pressure chamber.

As shown in FIG. 4A, the discharge channel 70 is a flow path that connects the communication flow path 72, the discharge pressure chamber 73, and the descender 74 in this order from the outlet of the manifold 60 to the discharge nozzle 75. Of these, the communication flow path 72 connects the manifold 60 and the discharge pressure chamber 73. The descender 74 connects the discharge pressure chamber 73 and the discharge nozzle 75. As described above, in the first piezoelectric element 71, the diaphragm 71a constitutes the wall portion of the discharge pressure chamber 73, is deformed by the application of the drive voltage, and ejects the ink in the discharge pressure chamber 73.

More specifically, the communication flow path 72 is a crank-shaped throttle flow path, and has high flow path resistance to ink. The communication flow path 72 directly connects the upper surface side of the manifold 60 and the lower surface side of the pressure chamber 73. One end 72a of the communication flow path 72 (corresponding to the outlet of the manifold 60) is connected to the left end of the manifold 60 from above. The communication flow path 72 extends upward from one end 72a and then bends to the right and extends. Further, the communication flow path 72 bends upward near the right end of the manifold 60 to reach the other end 72b. The other end 72b is connected to one end 73a of the discharge pressure chamber 73 from below.

The discharge pressure chamber 73 is a space extending from one end portion 73a to the right other end portion 73b, and is elongated in the left-right direction. The upper surface of the discharge pressure chamber 73 is an open surface, but is sealed with a diaphragm 71a as described above.

The descender 74 is a substantially straight flow path, and connects the lower surface side of the discharge pressure chamber 73 and the discharge nozzle 75. One end 74a of the descender 74 is connected to the other end 73b of the pressure chamber 73 from below. The descender 74 extends downward from one end 74a to reach the other end 74b. A discharge nozzle 75 is connected to the other end 74b. With the descender 74, the manifold 60 can be made deeper and the flow path resistance to the ink can be easily reduced.

Here, when the first piezoelectric element 71 is driven, the ink in the discharge pressure chamber 73 is pressurized and discharged from the discharge nozzle 75.

The dummy channel 80 does not have a communication flow path, as shown in FIG. 4 (b). The dummy channel 80 is an isolated flow path leading to the dummy nozzle 85 via the non-discharge pressure chamber 83 and the descender 84. Therefore, the non-discharge pressure chamber 83 is not filled with ink. The arrangement of the other flow path components including the second piezoelectric element 81 is the same as that of the discharge channel 70 described above. The second piezoelectric element 81 has the same form in which the diaphragm 81a constitutes the wall portion of the non-discharge pressure chamber 83. The second piezoelectric element 81 is deformed when energized, and the volume of the non-discharge pressure chamber 83 can be changed.

The components of each flow path such as the manifold 60 excluding the piezoelectric element and the pressure chamber are formed by laminating a plurality of plates having through holes, dents, grooves, etc., so that the laminated body (flow path member) 13a of these plates is laminated. Formed inside. At this time, the lower surface of the laminated body 13a is the nozzle surface 13b, and all the nozzles 75 and 85 are open. Further, in FIG. 4, the boundary (joint surface) of each plate constituting the laminated body 13a is not shown.

Further, in the channel row, the plurality of discharge channels 70 have the same dimensions of the communication flow path 72, the pressure chamber 73, the descender 74, and the discharge nozzle 75. And each of these dimensions is substantially the same as each dimension of the corresponding component of the dummy channel 80.

As described above, in the channel row, the dummy channel 80 is adjacent to the discharge channel 70 at the end end from the outside. The dummy channel 80 has the same configuration as the discharge channel 70. Therefore, the discharge characteristics can be made uniform between the discharge channel 70 at the end and the other discharge channels 70.

FIG. 5 is a diagram showing an electrical configuration of the recording head 13, and FIG. 5A shows a connection mode between the first and second piezoelectric elements 71 and 81 and the head driver IC 48. FIG. 5B shows the waveforms of the first and second drive voltages VD1 and VD2 applied to the first and second piezoelectric elements 71 and 81 that are in a positional relationship with each other.

Referring to FIGS. 4A to 5B, in the channel sequence, the plurality of first piezoelectric elements 71 and the second piezoelectric elements 81 at both ends (only the rear end is shown in FIG. 5A) are flat. It is connected to the head driver IC 48 by the wiring 78 and the wiring 88 of the type flexible substrate (for example, the flexible substrate). The head driver IC 48 is a collection of individual drivers.

If the first and second piezoelectric elements 71 and 81 are in a positional relationship with each other, the corresponding individual drivers are controlled by the same control signal VI. In addition, in the present embodiment, the value related to the second piezoelectric element is increased with respect to at least one of the capacitance of the piezoelectric element and the internal resistance of the individual driver. Therefore, as shown in FIG. 5B, the first drive voltage VD1 is applied to the first piezoelectric element 71, and the second drive voltage VD2 is applied to the second piezoelectric element 81.

The waveform shown by the dotted line in FIG. 5B is a waveform defined by the timing ti at which the second drive voltage VD2 starts to change. This waveform is the same as the control signal VI described above, except for the difference in voltage.

The first drive voltage VD1 and the second drive voltage VD2 are pulse-shaped voltages that change between the first potential v1 and the second potential v2, as described above. The waveforms of each pulse are trapezoidal, but there are differences in the rise time tr and the fall time tf. Specifically, the second drive voltage VD2 is longer for both the two time trs and tf. In FIG. 5B, in order to emphasize this difference, the waveform of the first drive voltage VD1 is drawn in a rectangular shape, and the waveform of the second drive voltage VD2 is drawn in a trapezoidal shape.

The reference numerals PWs, PWm, and PWl in FIG. 5B mean that the droplet sizes are "small ball", "medium ball", and "large ball" in order, and pulse waveforms corresponding to each are used. Shows.

FIG. 6 is an equivalent circuit diagram for each channel when the piezoelectric element is connected to the head driver IC 48, and FIG. 6A shows a set of the first piezoelectric element 71 and an individual driver for driving the first piezoelectric element 71 (individual driver 48A). It is a corresponding circuit diagram, and FIG. 6B is a circuit diagram corresponding to a set of a second piezoelectric element 81 and an individual driver for driving the second piezoelectric element 81 (individual driver 48B).

The individual driver 48A (first voltage application circuit of the present invention) has an internal resistance R1 and applies a first drive voltage VD1 to the first piezoelectric element 71. The first piezoelectric element 71 has a capacitance C1 and is also a kind of capacitor. The pair of the individual driver 48A and the first piezoelectric element 71 constitutes the first circuit 100A.

At this time, the first circuit 100A has a time constant τ1 (= C1 * R1) defined by C1 and R1. Reference numeral VI1 indicates a control signal applied to the individual driver 48A. This control signal VI1 is composed of a rectangular pulse wave.

When the control signal VI1 is applied to the individual driver 48A in the first circuit 100A, this signal VI1 is amplified to the voltage of the first drive voltage VD1 and applied to the first piezoelectric element 71. The first drive voltage VD1 is a rectangular wave when the load is open. However, when applied to the first piezoelectric element 71, the waveform is defined by the time constant τ1, so that the first drive voltage VD1 becomes a substantially trapezoidal wave having a rise time tr and a fall time tf. In FIG. 5B, in order to emphasize that the rise time tr and the fall time tf are short, these are omitted and the first drive voltage VD1 is shown as a rectangular wave.

The individual driver 48B (second voltage application circuit of the present invention) has an internal resistance R2 and applies a second drive voltage VD2 to the second piezoelectric element 81. The second piezoelectric element 81 has a capacitance C2 and is also a kind of capacitor. The pair of the individual driver 48B and the second piezoelectric element 81 constitutes the second circuit 100B.

At this time, the second circuit 100B has a time constant τ2 (= C2 * R2> τ1) defined by C2 and R2. Reference numeral VI2 indicates a control signal applied to the individual driver 48B. This control signal VI2 is composed of a rectangular pulse wave. If the first and second piezoelectric elements 71 and 81 are in a positional relationship next to each other, this control signal VI2 is the same as the control signal VI1.

When the control signal VI2 is applied to the individual driver 48B in the second circuit 100B, this signal VI2 is amplified to the voltage of the second drive voltage VD2 and applied to the second piezoelectric element 81. Here, since there is a magnitude relationship of τ2> τ1 with respect to the time constant, the rise time tr and the fall time tf of the second drive voltage VD2 are longer than those of the first drive voltage VD1. In FIG. 5B, the second drive voltage VD2 is shown as a trapezoidal wave in order to emphasize this relationship.

In order to structurally realize the magnitude relationship of τ2> τ1 with respect to the time constant, the internal resistance R2 of the individual driver 48B is made larger than that of the individual driver 48A, and the capacitance C2 of the second piezoelectric element 81 is set to the first piezoelectric element 71. There are three possible forms: the internal resistance R2 and the capacitance C2 are made larger than that of the above. The same effect can be obtained in either form, but first, a form in which the capacity value is adjusted will be described.

FIG. 7 is a schematic plan view showing the difference between the individual electrodes of the piezoelectric element, which is a form of capacitance value adjustment. FIG. 7A is a plan view showing the individual electrodes of the first piezoelectric element, and FIG. 7B is a plan view showing the individual electrodes of the second piezoelectric element. FIG. 7 shows an arrangement of the pressure chamber and the individual electrodes, and the components such as the diaphragm, the piezoelectric layer, and the common electrode are omitted for each piezoelectric element.

Referring to FIGS. 7 (a) and 7 (b), the discharge pressure chamber 73 and the non-discharge pressure chamber 83 have the same size and shape. On the other hand, the individual electrodes of the piezoelectric element differ in the shape in a plan view. In the first piezoelectric element 71 of the discharge pressure chamber 73, the deformation efficiency of the first piezoelectric element 71 is emphasized, and the individual electrodes 77 have a predetermined size and shape. In the predetermined direction 110 (the extending direction of the manifold 60, which is the front-rear direction on the carriage), the size of the individual electrode 77 is approximately 70% of the opening of the discharge pressure chamber 73, which is one size smaller than the size of the opening.

In the present embodiment, the dimensions L1 and L2 of the individual electrodes 77 and 87 in the predetermined direction 110 are different for the two piezoelectric elements 71 and 81. At this time, there is a relationship of L1 <L2. On the other hand, the dimensions W1 and W2 in the direction perpendicular to this (the left-right direction on the carriage) are the same. This difference in shape expands the active portion (area of the individual electrode 87) involved in the deformation of the second piezoelectric element 81, resulting in a decrease in deformation efficiency and an increase in the capacitance value C.

When the size of the active portion exceeds a suitable magnitude relationship with respect to the opening of the non-discharge pressure chamber 83, the excessively enlarged portion tends to be deformed in the direction opposite to the deformation direction of the remaining active portion. The second piezoelectric element 81 is prevented from being deformed in a desired direction, and the amount of deformation is reduced. At the same time, since the individual electrode 87 is expanded, the capacitance C2 of the second piezoelectric element 81 becomes larger than the capacitance C1 of the first piezoelectric element. With respect to the time constant, a magnitude relationship of τ2> τ1 is created.

[Action and effect of droplet ejection device]
FIG. 8 shows the drive voltage applied to the piezoelectric element with a dotted line for an empty pressure chamber, and shows the displacement of the corresponding piezoelectric element with a solid line.

As shown in FIG. 8, when the pressure chamber is not filled with the recording liquid, a large overshoot (excess) is applied when a rectangular wavy driving voltage that changes sharply (the rise time tr and the fall time tf are very short) is applied. Vibration of the piezoelectric element accompanied by deformation) occurs. In some cases, excessive deformation may damage the piezoelectric element, leading to failure.

However, in the present embodiment, the second drive voltage VD2 is adjusted for the non-discharge pressure chamber 83 so that the second piezoelectric element 81 is not excessively deformed. Specifically, the second drive voltage VD2 has a longer rise time tr and fall time tf than the first drive voltage VD1. Therefore, in the non-discharge pressure chamber 83, the second piezoelectric element 81 is not steeply displaced, so that excessive deformation thereof is suppressed.

Further, the second drive voltage VD2 has the same voltage as the first drive voltage VD1. The two adjacent piezoelectric elements 71 and 81 have the same amount of displacement when a drive voltage is applied. Therefore, the discharge characteristics are uniform among the discharge channels 70.

Further, in the present embodiment, if the first piezoelectric element 71 and the second piezoelectric element 81 are adjacent to each other, the same control signal VI is supplied to the corresponding individual driver. That is, it is not necessary to prepare a new control signal in order to drive the second piezoelectric element 81.

<Modification 1>
In the first modification, in the first embodiment, the second drive voltage VD2 has a smaller pulse amplitude (voltage) than the first drive voltage VD1. For the amplitude adjustment, the individual driver 48B may be smaller than the individual driver 48A in terms of the amplification factor of the control signal.

According to this modification 1, even if the second drive voltage VD2 is a rectangular wave that changes sharply, the excessive deformation is weakened by the small amplitude. Further, the same control signal VI may be input to the adjacent drivers 48A and 48B. Therefore, control is easy, and it is not necessary to prepare a new control signal VI for the second piezoelectric element.

<Modification 2>
In the second modification, in the first embodiment, in the second circuit 100B, the capacitance C2 of the second piezoelectric element 81 is the same as the capacitance C1 of the first piezoelectric element 71. Moreover, the internal resistance R2 of the individual driver 48B is set to be larger than the internal resistance R1 of the individual driver 48A. A protection resistor is connected in series to the output terminal of the head driver IC 48, and the protection resistance for the individual driver 48B may be made larger than that for the individual driver 48A.

Further, although the second piezoelectric element 81 has the same capacity as the first piezoelectric element 71, it is effective to change the shape of the active portion (individual electrode) of the piezoelectric element as described in the first embodiment. Specifically, regarding the area, there is a relationship of L1 * W1 = L2 * W2. At this time, with respect to the piezoelectric elements 71 and 81 that are adjacent to each other, the dimensions L1 and L2 in the predetermined direction 110 have a magnitude relationship of L1 <L2. Moreover, the dimensions W1 and W2 have a magnitude relationship of W1> W2 in the direction orthogonal to the predetermined direction 110. In this embodiment, the above-mentioned excessively enlarged portion is generated in the active portion of the second piezoelectric element 81.

According to this modification 2, the time constant τ2 of the second circuit 100B can be preferably set to be larger than the time constant τ1 of the first circuit 100A. Further, since the second piezoelectric element 81 has the same capacity as the first piezoelectric element 71, as described in the first embodiment, the deformation efficiency of the second piezoelectric element 81 can be changed by changing the shape of the active portion (individual electrode). Can be structurally suppressed.

<Modification 3>
In the third modification, in the first embodiment, in the second circuit 100B, the capacitance C2 of the second piezoelectric element 81 is larger than the capacitance C1 of the first piezoelectric element 71. Moreover, the internal resistance R2 of the individual driver 48B is also set to be larger than the internal resistance R1 of the individual driver 48A.

According to this modification 3, more preferably, the time constant τ2 of the second circuit 100B can be set larger than the time constant τ1 of the first circuit 100A.

(Embodiment 2)
FIG. 9 is a diagram schematically showing the configuration of the droplet ejection device according to the second embodiment of the present invention. Mainly, the vicinity of the piezoelectric element of the recording head is shown. FIG. 9A is a plan view of the vicinity of the piezoelectric element. FIG. 9B is a cross-sectional view taken along the cutting line IXb-IXb in the vicinity of the piezoelectric element.

The droplet ejection device of the second embodiment is different from the droplet ejection device of the first embodiment in the form of the non-ejection pressure chamber and the corresponding piezoelectric element, and the other configurations are the droplet ejection device of the first embodiment. It is the same. Hereinafter, this difference will be described.

Referring to FIGS. 9 (a) and 9 (b), in the second embodiment, a plurality of (three in this case) non-discharge pressure chambers 83 are arranged at both ends of the channel row. Then, one second piezoelectric element 81 is arranged so as to straddle the plurality of non-discharge pressure chambers 83.

In addition, in order to make the figure easier to see, the illustration of the diaphragm is omitted. The diaphragm is a thin plate-like member that seals the opening of the pressure chamber, but individual diaphragms may be arranged for each pressure chamber, or one diaphragm is commonly arranged for all pressure chambers. May be.

Specifically, in the channel row, both ends are each composed of three dummy channels 80. In one discharge channel 70, one individual electrode 77 is arranged on the upper side of one discharge pressure chamber 73 via a diaphragm (not shown). On the other hand, in the three dummy channels 80, one individual electrode 87 is arranged on the upper side of the three non-discharge pressure chambers 83 via a diaphragm (not shown).

These individual electrodes 77 and 87 are covered with one piezoelectric layer 92. The piezoelectric layer 92 is provided with a plurality of slits 92a. The slit 92a is located between the individual electrodes 77 and between the individual electrodes 77 and the individual electrode 87, but does not divide the piezoelectric layer 92. As a result, the piezoelectric elements 71 and 81 are functionally separated and selectively driven.

A common electrode 91 is provided so as to cover the slit and the piezoelectric layer 92. The common electrode 91 is connected to the ground of the head driver IC 48. One individual electrode 77, the piezoelectric layer 92, and the common electrode 91 constitute one first piezoelectric element 71, and one individual electrode 87, the piezoelectric layer 92, and the common electrode 91 constitute one second piezoelectric element 81. are doing.

According to the second embodiment, three non-discharge pressure chambers 83 are arranged on both sides of the arrangement of the discharge pressure chambers 73 at the same intervals as the discharge pressure chambers 73, so that the discharge is located at least at the end of the arrangement. The pressure chamber 73 ensures that structural crosstalk received from the surroundings is alleviated.

At this time, one second piezoelectric element 81 surely has a larger capacity C2 than one adjacent first piezoelectric element 71. Therefore, for the time constant, the magnitude relation of τ2> τ1 holds. Therefore, even if the non-discharge pressure chamber 83 is not filled with the recording liquid, excessive deformation of the second piezoelectric element 81 can be more preferably suppressed.

In the above configuration, the magnitude relation of τ2> τ1 is structurally realized for the time constant. In both adjustment methods, the rise time tr and the fall time tf of the second drive voltage VD2 are similarly adjusted at the same time. However, the degree of adjustment may be different between the rise time tr and the fall time tf.

The form of the second piezoelectric element 81 changes between a relaxed state and a tense state due to a change in the driving voltage. For example, in a tense state, the second piezoelectric element 81 is convexly deformed inward of the non-discharge pressure chamber 83.

Therefore, when the form of the second piezoelectric element 81 shifts from the relaxed state to the tense state, the rise time tr or the fall time tf of the second drive voltage VD2 is made longer than that of the first drive voltage VD1. On the other hand, when the form of the second piezoelectric element 81 shifts in the opposite direction, the fall time tf or rise time tr of the second drive voltage VD2 is changed to the rise time tr or fall when shifting from the relaxed state to the tension state. The fall time tf or the rise time tr or more of the first drive voltage VD1 is set within a range not exceeding the time tf.

According to this configuration, the relaxation effect of the non-discharge pressure chamber 83 on the structural crosstalk is higher than when the rise time tr and the fall time tf of the second drive voltage VD2 are adjusted as described above. It can be said that it will be. Further, when the second piezoelectric element 81 shifts from the relaxed state to the tense state, it is more likely to cause excessive deformation than when it shifts in the opposite direction. Here, the second drive voltage VD2 has a longer rise time tr or fall time tf. Therefore, when shifting from the relaxed state to the tense state, the steepness of the change is suppressed, and the damage to the second piezoelectric element 81 is effectively suppressed.

In this case, a circuit that generates the second drive voltage VD2 having this specific waveform is required. Since such a circuit is well known, the description thereof will be omitted.

Further, in the above examples and modifications, the dummy channel has been described as a flow path having no communication flow path. However, the dummy channel may have a communication flow path. In this case, any component other than the non-discharge pressure chamber may be missing or cut off. For example, if there is no dummy nozzle, if there is a descender, the middle part of the descender is cut off, the connection with the non-discharge pressure chamber is not made, the form without the descender itself, or even if there is a communication flow path. It is conceivable that the non-discharge pressure chamber is not filled with ink, such as a form in which the non-discharge pressure chamber is not connected.

From the above description, many improvements and other embodiments will be apparent to those skilled in the art. Therefore, the above description should be construed as an example only.

The droplet ejection device of the present invention is useful as a droplet ejection device capable of suppressing excessive deformation of the piezoelectric element due to the non-discharge pressure chamber not being filled with the recording liquid.

1 Droplet ejection device 10 Paper feed tray 11 Platen 12 Carriage 13 Recording head 13a Laminated body 48 Head driver IC
48A, 48B Individual driver 60 Manifold 71 1st piezoelectric element 73 Discharge pressure chamber 77 Individual electrode 81 2nd piezoelectric element 83 Non-discharge pressure chamber 87 Individual electrode 100A 1st circuit 100B 2nd circuit 110 Predetermined direction VD1 1st drive voltage VD2 1st 2 Drive voltage tr Rise time tf Rise time v1 1st potential v2 2nd potential

Claims (8)

A flow path member in which a plurality of discharge pressure chambers arranged in a row and a pair of non-discharge pressure chambers arranged so as to sandwich the plurality of discharge pressure chambers in a direction in which the plurality of discharge pressure chambers are arranged are formed. ,
A plurality of first piezoelectric elements arranged corresponding to the plurality of discharge pressure chambers and to which a pulsed first drive voltage is applied.
A recording head comprising a pair of second piezoelectric elements, each of which is disposed corresponding to the pair of non-discharge pressure chambers and to which a pulsed second drive voltage is applied.
The pair of non-discharge pressure chambers were not filled with the recording liquid, and the recording liquid was not filled.
At the first drive voltage in which at least one of the fall time and the rise time of the second drive voltage is applied to the first piezoelectric element adjacent to the second piezoelectric element, the fall of the second drive voltage. Longer than at least one of the fall and rise times corresponding to at least one of the time and rise time
The second drive voltage is a droplet ejection device having a smaller pulse amplitude than the first drive voltage. A flow path member in which a plurality of discharge pressure chambers arranged in a row and a pair of non-discharge pressure chambers arranged so as to sandwich the plurality of discharge pressure chambers in a direction in which the plurality of discharge pressure chambers are arranged are formed. ,
A plurality of first piezoelectric elements arranged corresponding to the plurality of discharge pressure chambers and to which a pulsed first drive voltage is applied.
A recording head comprising a pair of second piezoelectric elements, each of which is disposed corresponding to the pair of non-discharge pressure chambers and to which a pulsed second drive voltage is applied.
The pair of non-discharge pressure chambers were not filled with the recording liquid, and the recording liquid was not filled.
At the first drive voltage in which at least one of the fall time and the rise time of the second drive voltage is applied to the first piezoelectric element adjacent to the second piezoelectric element, the fall of the second drive voltage. Longer than at least one of the fall and rise times corresponding to at least one of the time and rise time
The recording head is
A plurality of first voltage application circuits for applying the first drive voltage to the first piezoelectric element, and
The second piezoelectric element is provided with two second voltage application circuits for applying the second drive voltage.
Droplet ejection in which the time constant of the second circuit created by the second piezoelectric element and the second voltage application circuit is larger than the time constant of the first circuit created by the first piezoelectric element and the first voltage application circuit. Device. A flow path member in which a plurality of discharge pressure chambers arranged in a row and a pair of non-discharge pressure chambers arranged so as to sandwich the plurality of discharge pressure chambers in a direction in which the plurality of discharge pressure chambers are arranged are formed. ,
A plurality of first piezoelectric elements arranged corresponding to the plurality of discharge pressure chambers and to which a pulsed first drive voltage is applied.
A recording head comprising a pair of second piezoelectric elements, each of which is disposed corresponding to the pair of non-discharge pressure chambers and to which a pulsed second drive voltage is applied.
The pair of non-discharge pressure chambers were not filled with the recording liquid, and the recording liquid was not filled.
At the first drive voltage in which at least one of the fall time and the rise time of the second drive voltage is applied to the first piezoelectric element adjacent to the second piezoelectric element, the fall of the second drive voltage. Longer than at least one of the fall and rise times corresponding to at least one of the time and rise time
In the flow path member, in the arrangement direction in which the plurality of discharge pressure chambers are arranged, a plurality of the non-discharge pressure chambers are formed on both sides of the plurality of discharge pressure chambers at intervals between the discharge pressure chambers.
A droplet ejection device in which one second piezoelectric element is arranged across the plurality of non-ejection pressure chambers. The second drive voltage is at least one of the first drive voltage applied to the first piezoelectric element adjacent to the second piezoelectric element to which the second drive voltage is applied, and the fall time and rise time. The droplet ejection device according to claim 3 , wherein the waveform defined by the start timing of the voltage change is the same except for. The second drive voltage is
It is a pulsed voltage that changes between the first potential v1 and the second potential v2 different from the first potential v1, and the potential of the second piezoelectric element applied to the second piezoelectric element is the said. When the first potential v1 is present, the volume of the non-discharge pressure chamber is the first volume V1, and when the potential of the second piezoelectric element is at the second potential v2, the volume of the non-discharge pressure chamber is the first volume. The second volume V2, which is smaller than the volume V1 of 1, is used, and the volume is V2.
The fall time or rise time of the second drive voltage until the potential changes from the first potential v1 to the second potential v2 is applied to the first piezoelectric element adjacent to the second piezoelectric element. The droplet ejection device according to any one of claims 1 to 3 , wherein the first drive voltage is longer than the fall time or rise time corresponding to the fall time or rise time of the second drive voltage. .. The second circuit is the droplet ejection device according to claim 2 , wherein the resistance of the second voltage application circuit is set to be larger than the resistance of the first voltage application circuit. The second circuit is the droplet ejection device according to claim 2 , wherein the capacity of the second piezoelectric element is set to be larger than the capacity of the first piezoelectric element. The non-discharge pressure chamber and the discharge pressure chamber have the same size and shape, and have the same size and shape.
The droplet ejection device according to claim 6, wherein the dimension of the electrode of the second piezoelectric element in a predetermined direction is larger than that of the first piezoelectric element.

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